Learn SwiftUI (Day 7/100)

Swift

• functions
• function parameter names
• return one value & return multiple values
• call function without explicit parameter name

Define functions

We need to write the parameter name as part of the function call. This isn’t common in other languages, but I think it’s really helpful in Swift as a reminder of what each parameter does.

func printTimesTables(number: Int, end: Int = 10) {
    for i in 1...end {
        print("\(i) x \(number) is \(i * number)")
    }
}
printTimesTables(number: 2)

With return value:

func rollDice() -> Int {
    return Int.random(in: 1...6)
}
for i in 1...6 {
    print("\(i): \(rollDice())")
}

Take a list of int as parameter:

func square(numbers: [Int]) {
    for number in numbers {
        let squared = number * number
        print("\(number) squared is \(squared).")
    }
}
square(numbers: [2, 3, 4])

Return an arrary:

func abc() -> [Int] {}

Return a dictionary:

func abc() -> [String: Int] {}

Return a tuple that contains multiple values:

func getUser() -> (firstName: String, lastName: String) {
    return (firstName: "John", lastName: "Doe")
}
let user = getUser()
print(user.firstName)
print(user.lastName)
// or
let (firstName, lastName) = getUser()
print(firstName)
print(lastName)

Or:

func getUser() -> (String, String) {
    return ("Taylor", "Swift")
}
let user = getUser()
print(user.0)
print(user.1)

Use _ to omit the parameter name:

func isUppercase(_ string: String) -> Bool {
    string == string.uppercased()
}

let string = "HELLO, WORLD"
let result = isUppercase(string)